Convert `Java.lang.String` TO `oracle.sql.TIMESTAMPTZ`

Your timestamps are not in a standard java parseable formats. So in order to parse them you need to write custom code for handling such formats.

Couple of observations:

Asia/Calcutta is not a valid Parseable TimeZone, hence you need some mechanism to get corresponding timezone.

8:00 is also not a valid Parseable Timezone in java, hence you need some mechanism to format it in a valid value +08:00

Keeping above points in mind, following code will do the needful for you.

    SimpleDateFormat dateFormatTZGeneral = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS z");
    SimpleDateFormat dateFormatTZISO = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS XXX");
    SimpleDateFormat dateFormatWithoutTZ = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");


    String[][] zoneStrings = DateFormatSymbols.getInstance().getZoneStrings();

    Date date = null;

    String[] timeStampSplits = timestamp.split(" ");
    if(timeStampSplits.length>2) {

        String timezone = timeStampSplits[2];
        //First Case Asia/Calcutta
        if(Character.isAlphabetic(timezone.charAt(timezone.length()-1))) {

            for(String[] zoneString: zoneStrings) {
                if(zoneString[0].equalsIgnoreCase(timezone)) {
                    timeStampSplits[2] = zoneString[2];
                    break;
                }
            }

            timestamp = createString(timeStampSplits," ");
            date = getDate(timestamp, dateFormatTZGeneral);
        } else {
            //Second Case 8:00
            timeStampSplits[2] = formatTimeZone(timeStampSplits[2]);

            timestamp = createString(timeStampSplits," ");
            date = getDate(timestamp, dateFormatTZISO);
        }

    } else {
        // Third Case without timezone
        date = getDate(timestamp, dateFormatWithoutTZ);
    }

    System.out.println(date);

    TIMESTAMPTZ oraTimeStamp = new TIMESTAMPTZ(<connection object>,new java.sql.Timestamp(date.getTime());

Above code uses following utility methods

private static Date getDate(String timestamp, SimpleDateFormat dateFormat) {
    Date date = null;
    try {
        date = dateFormat.parse(timestamp);
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return date;
}

private static String createString(String[] contents, String separator) {
    StringBuilder builder = new StringBuilder();
    for (String content : contents) {
        builder.append(content).append(separator);
    }
    builder.deleteCharAt(builder.length()-separator.length());

    return builder.toString();
}

private static String formatTimeZone(String timeZone) {
    String[] timeZoneSplits = timeZone.split(":");
    DecimalFormat formatter = new DecimalFormat("+##;-#");
    formatter.setMinimumIntegerDigits(2);

    timeZoneSplits[0] = formatter.format(Integer.parseInt(timeZoneSplits[0]));
    return createString(timeZoneSplits, ":");
}

This code is specifically written to cater your timestamp examples, any deviation might not be handled by this and it will need more customization.

Hope this helps you.